A political action committee created to encourage Hillary Rodham Clinton to run for president received its first congressional endorsement on Tuesday.

In a statement released by Ready for Hillary PAC, which launched shortly after the 2012 elections, Missouri Sen. Claire McCaskill endorsed the group's effort to lay a political groundwork for the former secretary of State to have at the ready should she decide to run.

McCaskill, who was an early endorser of President Barack Obama in the 2008 campaign, called the effort "critical" to Clinton's potential for success in 2016.

"They aren’t only reaching out to folks who supported Hillary in 2008," McCaskill said. "They’re helping to show that regardless of who you supported for President back then, we can all agree today that there is nobody better equipped to be our next President than Hillary Clinton."

The PAC was started by former Clinton staffers and supporters, and it has picked up some endorsements from more high-profile Clinton loyalists in its first months. Craig T. Smith, a former White House political director under President Bill Clinton, is now listed as a senior adviser.

"Ready for Hillary is fortunate to have such a powerful and respected leader like Claire joining our grassroots team," Smith said in a statement.